Amphibious. The dragon can breathe air and water.

Innate Spellcasting. The dragon's innate spellcasting ability is Wisdom (spell save DC 19, +11 to hit with spell attacks). It can innately cast the following spells, requiring no material components:

At will: detect magic, earth tremor, invisibility
3/day each: greater invisibility, hypnotic pattern

Legendary Resistance (3/Day). If the dragon fails a saving throw, it can choose to succeed instead.

Multiattack. The dragon can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 17 (2d10 + 6) piercing damage plus 4 (1d8) force damage.

Claw. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 13 (2d6 + 6) slashing damage.

Tail. Melee Weapon Attack: +9 to hit, reach 15 ft., one target. Hit: 15 (2d8 + 6) bludgeoning damage.

Frightful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 19 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Frightful Presence for the next 24 hours.

Concussive Force Blast (Recharge 5–6). The dragon blasts a concussive force in a 30-­foot cone. Each creature in that line must make a DC 18 Dexterity saving throw, taking 54 (12d8) force damage on a failed save, or half as much damage on a successful one. The creature must then make a DC 17 strength save or be knocked prone.

Crystalline Lozenge. The dragon spits a crystalline lozenge up to 50 feet away that explodes on impact. Any creature within a 30 foot radius of the Lozenge upon impact must make a DC 20 dexterity save or take 18 (6d6) piercing damage plus 10 (3d8) force damage on a failed save, taking half as much on a successful one, and become stunned until the beginning of the dragon's next turn. The dragon cannot use this attack again until it has rested long enough to consume the amethyst crystals needed to create the lozenge.

The dragon can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The dragon regains spent legendary actions at the start of its turn.

Detect. The dragon makes a Wisdom (Perception) check.

Tail Attack. The dragon makes a tail attack.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 10 feet of the dragon must succeed on a DC 19 Dexterity saving throw or take 13 (2d6 + 6) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.